A device for blocking spectacle lenses is generally known from document U.S. Publication No. 2005/0139309. The device comprises an imaging/aligning station, a measuring station and a blocking station generally in an arrangement alongside one another or in succession, between which stations the spectacle lenses can be automatically transported by a transport system with a spectacle lens mounting head. The imaging/aligning station has a geometrically defined spectacle lens support on which a supported spectacle lens to be blocked can be manually aligned by rotation and/or displacement as desired or as required per prescription. The aligned spectacle lens to be blocked can be mechanically measured in the measuring station at its face at which it is to be blocked. On the other hand, the blocking station has a block piece mount in which a block piece or blocking ring is mounted in centered manner before the aligned spectacle lens is blocked on the block piece by the mentioned face by using a temporarily deformable blocking material, here an optically hardenable adhesive.
The transport system is in that case in a position of gripping and holding the spectacle lens, which is aligned in the imaging/aligning station, at its other face by the spectacle lens mounting head, then bringing it into a defined position above the measuring station and later the blocking station (horizontal CNC linear axis) and lowering the aligned spectacle lens in a defined manner at the respective station (vertical CNC linear axis) for it to be measured or blocked on the block piece. In that regard, a feature is that the spectacle lens is positioned by the transport system in defined manner, i.e. at any preselectable height above the block piece, and during the blocking can be held in the defined relative position with respect to the block piece while leaving a blocking material receiving gap between spectacle lens and block piece (also termed “spatial blocking”).
A significant advantage of this procedure is that the spectacle lens can be freely positioned in three dimensions in relation to the block piece, thus during blocking never experiences constrained orientation by the block piece, as a result of which also accuracy during blocking of the spectacle lens is increased. The latter concerns, in particular, progressive lenses often referred to as PALs, in which it can be very difficult to correctly set these if they are supported on conventional circular blocking rings, because the progressive curve is not spherical and the spectacle lens is thus not seated fully or is seated loosely on the blocking ring. On the other hand, in the case of “spatial blocking” it is possible to realize in problem-free manner, for example, a desired angular orientation, tilting and/or displacement of the spectacle lens relative to the block piece for, for example, prismatic blocking. In addition, the thickness of the layer of blocking material or adhesive between spectacle lens and block piece is basically freely selectable in the case of “spatial blocking” so that, for example, there is avoidance of the risk of no blocking material being present at specific locations between spectacle lens and block piece because the blocking material could not reach there. In this way, a whole-area support and adhesion/glueing of the spectacle lens can be guaranteed for processing of the blocked spectacle lens at the surface and/or edge. Equally, it is possible to avoid undesired free gaps between spectacle lens and block piece in which liquid, in a given case as the consequence of capillary effects, could collect, which can lead to problems during coating (outgassing under vacuum) if the spectacle lens in the production process is to remain throughout on the block piece, such as described in, for example, document U.S. Pat. No. 8,905,388.
In addition, it was proposed in document U.S. Pat. No. 8,616,150 to develop the relevant category of prior art—also in the sense of widest possible automation of the blocking process for production of spectacle lenses on an industrial scale—in such a way that the transport system is in a position of positioning the spectacle lens, which is to be blocked, not only in two directions, but fully in three dimensions, before it is blocked on the block piece. However, this requires six CNC movement axes, namely three CNC linear axes substantially perpendicular to one another and three CNC rotational or tilt axes about these linear axes.
However, such CNC blockers—even with only two CNC movement axes—represent a substantial capital cost, need a relatively large installation area and as such are over-dimensioned for smaller prescription workshops as determined by reference to the spectacle lens throughput thereof.
Obviously, smaller blockers have already been proposed—see, for example, document U.S. Publication No. 2014/0315472—which are accordingly more advantageous and also require only a comparatively small installation area. However, in this prior art the spectacle lenses to be blocked are aligned at the block piece, which significantly restricts the possible relative settings of the spectacle lens with respect to the block piece. Shape-adapted block pieces were created here as a remedy, but this is with considerable outlay with respect to production and stocking of the different block pieces. Genuine “spatial blocking” in the above sense is not possible with these prior art blockers.
Accordingly, it is desired to create a simplest and most economic and compact device possible for the blocking of workpieces, particularly spectacle lenses, for processing and/or coating thereof even in smaller workshops, in which the workpiece is not subject to any significant restrictions with respect to its position relative to the block piece.